PTL 1 and PTL 2 disclose mixing a base powder containing an iron-based powder with a machinability-improving powder in order to provide a sintered body with improved machinability, pressing the mixed powder to form a compact, and sintering the compact to form a sintered body. As specific examples of the machinability-improving powder, PTL 1 discloses manganese sulfide (MnS) powder and boron nitride (BN) powder, and PTL 2 discloses anorthite powder and gehlenite powder, which are CaO—Al2O3—SiO2-based composite oxide powders.